Malaysia's acting Transport Minister Hishammuddin Hussein holds satellite images as he speaks about the search for the missing Malaysia Airlines flight MH370 on March 26.

A satellite photo, showing the locations and co-ordinates of unknown objects reported by the Malaysian Remote Sensing Agency (MRSA) in the Indian Ocean. The images were taken on March 23 and released on March 26.

A satellite photo, showing the location of unknown objects reported by the Malaysian Remote Sensing Agency (MRSA) in the Indian Ocean. The images were taken on March 23 and released on March 26.

Solid matter is pictured floating in the southern Indian Ocean seen from a Royal New Zealand Air Force P-3K2 Orion aircraft searching for missing Malaysian Airlines flight MH370.

INDIAN OCEAN - This handout Satellite image made available by the AMSA (Australian Maritime Safety Authority) shows a map of the planned search area for missing Malaysian Airlines Flight MH370 on March 24, 2014.

A still image taken from video shows an image of an object spotted in the southern Indian Ocean by the Gaofen-1 high-resolution optical Earth observation satellite of CNSA.

Malaysia's acting Transport Minister Hishammuddin Hussein holds up a note that he has just received on a new lead in the search for the missing Malaysia Airlines Flight MH370, during a news conference at Kuala Lumpur International Airport March 22, 2014.

Family members of passengers onboard Malaysia Airlines Flight MH370 raise their fists as they shout "return our families" to protest against the lack of new information after a routine briefing given by Malaysia's government and military representatives at Lido Hotel in Beijing March 22, 2014.

Map of the southern Indian Ocean locating site where a satellite may have found debris related to Malaysia Airlines Flight 370; includes satellite images of possible debris. MCT

Satellite photos from March 20 show the objects "possibly associated" with the search for the missing plane. The images were released hours after Australia announced it had "credible" leads in the search for flight MH370.

Satellite photos from March 20 show the objects "possibly associated" with the search for the missing plane. The images were released hours after Australia announced it had "credible" leads in the search for flight MH370.

A crew member aboard a Royal Australian Air Force (RAAF) AP-3C Orion uses binoculars as it flies over the southern Indian Ocean during the search for missing Malaysian Airlines flight MH370 March 22, 2014.

Pilot Dave Smith (R) gives a pre-flight briefing aboard a Royal New Zealand Air Force P-3K2 Orion aircraft before taking off to search for missing Malaysian Airlines flight MH370, at RAAF base Pearce near Perth, March 22, 2014.

The Arleigh Burke-class guided-missile destroyers USS Kidd and USS Pinckney are seen en transit in the Pacific Ocean in this US Navy picture taken May 18, 2011. Kidd and Pinkney have been searching for the missing Malaysian airliner and are being re-deployed to the Strait of Malacca off Malaysia's west coast as new search areas are opened in the Indian Ocean.

A crew member from the Royal Malaysian Air Force looks through the window of a Malaysian Air Force CN235 aircraft during a Search and Rescue operation to find the missing Malaysia Airlines flight MH370.

A family member of a passenger onboard Malaysia Airlines Flight MH370 covers her face as she cries after a routine briefing given by Malaysia Airlines at Lido Hotel in Beijing, March 22, 2014.

A family member of a passenger onboard the missing Malaysia Airlines flight MH370 cries as he watches a message board dedicated to passengers.

Malaysia's acting Transport Minister Hishammuddin Hussein shows two maps with corridors of the last known possible location of the missing plane.

Chinese relatives of the missing passengers who were travelling onboard Malaysia Airlines flight MH370 watch a television displaying a Malaysian press conference at Lido Hotel in Beijing.

Students watch as a group of artists put the finishing touches to a three dimensional artwork at a school in Makati city, metro Manila. According to the artists, the artwork is their way of expressing sympathy towards the relatives of passengers onboard the missing Boeing 777-200ER.

Students from an international school in east China city Zhuji pray for the passengers onboard Malaysia Airlines flight MH370.

Satellite images reveal a possible crash site for the missing Malaysia Airlines plane, where three large objects were seen in the water.

Indian sand artist Sudarshan Pattnaik works on a sand sculpture of missing Malaysia Airlines flight MH370, at golden beach at Puri in the eastern Indian state of Odisha.

A charity worker comforts an emotional relative of a passenger.

LOOKING FOR ANSWERS: Family members of missing passengers leave a meeting in a Beijing Hotel.

MESSAGE OF HOPE: A Vietnamese tourist writes a message of hope for missing passengers and crew.

MESSAGES FOR THE MISSING: Tying a message of hope on a message board for passengers and crew.

Military personnel look out of a Singapore Air Force plane during the search.

A combination photo shows two men whom police said were travelling on stolen passports onboard the missing Malaysia Airlines MH370 plane.

A Chinese relative of a passenger of Malaysia Airlines MH370 is comforted by a staff member of the airport as she shields her face from journalists at Kuala Lumpur International Airport.

People believed to be relatives of passengers of the missing Malaysia Airlines flight MH370 are escorted to the VIP section of the Beijing Capital International Airport prior to flying to Kuala Lumpur.

A family member of a passenger from the missing Malaysia Airlines flight MH370 waits for news at Lido Hotel on March 10, in Beijing, China. Investigative teams continue to search for the missing Malaysia Airlines flight MH370 and the 293 passengers that were travelling from Kuala Lumpur to Beijing.

Dato' Azharuddin Abdul Rahman, director general of the Malaysian Department of Civil Aviation briefs the media over latest updates on missing Malaysia Airline MH370 on March 10, in Kuala Lumpur.

An officer looks out of a helicopter during a mission to find the Malaysia Airlines flight MH370 that disappeared from radar screens in the early hours of Saturday, near Tho Chu Island.

A map of a flight plan is seen on a computer screen during a meeting before a mission to find the Malaysia Airlines flight MH370 that disappeared from radar screens in the early hours of Saturday, at Phu Quoc Airport.

A woman stands in front of a giant screen showing the number hours since Malaysia Airlines flight MH370 went missing, in Beijing on March 10.

Relatives of a passenger onboard the missing Malaysia Airlines flight MH370 cry inside a hotel they are staying, in Putrajaya. China has urged Malaysia to step up the search for the jetliner that went missing with 239 people on board, about two-thirds of them Chinese, and said it has sent security agents to help with an investigation into the misuse of passports.

Journalists place their recorders as they get ready for the first briefing of the day at a news conference at the Kuala Lumpur International Airport in Sepang on March 10.

Life vests and lifesavers are seen onboard a Vietnam Air Force search and rescue aircraft on a mission to find the missing Malaysia Airlines flight MH370, off Tho Chu island.

Indian sand artist Sudarshan Patnaik applies the final touches to a sand art sculpture he created wishing for the well being of the passengers of Malaysian Airlines flight MH370, on a beach in Puri, in the eastern Indian state of Odisha.

A relative (left) of a passenger of Malaysia Airlines flight MH370 is escorted by a caregiver from Malaysia Airlines as they walk in a corridor at a hotel in Beijing.

Admiral Datuk Mohd Amdan Kurish, Director General of the Malaysian Maritime Enforcement Agency, looks at a radar screen while searching for a missing Malaysia Airlines plane in the South China Sea.

A view of oil slicks (pale line near the bottom right) spotted in an area of the South China Sea about 100 nautical miles (185 km) from Tok Bali Beach in Malaysia's Kelantan state.

An aerial view of an oil spill is seen from a Vietnamese Air Force aircraft in the search area for a missing Malaysia Airlines plane, 250 km from Vietnam and 190 km from Malaysia, in this handout photo from Thanh Nien Newpaper taken on March 8.

Volunteer rescue workers and religious organisations pray during multi-religion mass prayers for the passengers of Malaysian Airlines flight MH370, at the Kuala Lumpur International Airport in Sepang.

Vietnamese Air Force officers sit in the cockpit of a search and rescue aircraft as they fly over the search area for a missing Malaysia Airlines plane.

A relative (front) of a passenger of Malaysia Airlines flight MH370 cries as she walks past journalists at a hotel in Beijing March 9, 2014. The Malaysia Airlines Boeing 777-200ER aircraft carrying 227 passengers and 12 crew was presumed to have crashed off the Vietnamese coast on Saturday.

Journalists attempt to interview a woman who is the relative of a passenger on Malaysia Airlines flight MH370, as she crouches on the floor crying, at the Beijing Capital International Airport.

The Malaysia Airlines flight carrying 227 passengers and 12 crew lost contact with air traffic controllers early on Saturday en route from Kuala Lumpur to Beijing, the airline said in a statement.

A spokesman (centre) of Malaysia Airlines is surrounded by journalists as he gives a briefing about Malaysia Airlines flight MH370, at a hotel in Beijing March 8, 2014.

A relative of a passenger onboard Malaysia Airlines flight MH370 cries, surrounded by journalists, at the Beijing Capital International Airport on March 8, 2014.

The search for a missing Malaysia Airlines jetliner expanded on Wednesday to cover a swathe of Southeast Asia, from the South China Sea to India’s territorial waters, with authorities no closer to explaining what happened to the plane or the 239 people on board.

Vietnam briefly scaled down search operations in waters off its southern coast, saying it was receiving scanty and confusing information from Malaysia over where the aircraft may have headed after it lost contact with air traffic control.

Hanoi later said the search — now in its fifth day — was back on in full force and was even extending on to land. China also said its air force would sweep areas in the sea, clarifying however that no searches over land were planned.

The seas off India’s Andaman and Nicobar Islands are also being combed for traces of the lost jet.

‘‘We are expanding to the east of the expected route of the flight and on land,’’ Lieutenant General Vo Van Tuan, Vietnam’s deputy army chief of staff and spokesman for its search and rescue committee, told reporters.

The confusion over where to look is adding to one of the most baffling mysteries in modern aviation history, and prolonging the agonising wait for hundreds of relatives of the missing.

Flight MH370 dropped out of sight an hour after taking off from Kuala Lumpur to Beijing early on Saturday, under clear night skies and with no suspicion of any mechanical problems.

Dozens of planes and ships have already searched tens of thousands of square miles of Malaysia and off both its coasts without finding a trace of the Boeing 777.

Adding to the frustration and uncertainty, Malaysia’s military has said the plane could have turned around from its planned flight path, but there were conflicting statements and reports about how far and in which direction it could have flown after communication was lost.

OFF COURSE?

Malaysia’s air force chief, Rodzali Daud, denied saying military radar had tracked MH370 flying over the Strait of Malacca off the country’s west coast, about 500 km (310 miles) from the point ,roughly midway between the east coast town of Kota Bharu and Vietnam, where it was last seen by air traffic control.

Malaysia’s Berita Harian newspaper on Tuesday quoted Rodzali as saying the plane was last detected at the northern end of the Strait of Malacca at 2.40 a.m. on Saturday, more than an hour after it lost contact.

‘‘It would not be appropriate for the Royal Malaysian Air Force to issue any official conclusions as to the aircraft’s flight path until a high amount of certainty and verification is achieved,’’ Rodzali said in a statement on Wednesday.

‘‘However all ongoing search operations are at the moment being conducted to cover all possible areas where the aircraft could have gone down in order to ensure no possibility is overlooked.’’

Indonesia and Thailand, which lie on either side of the northern part of the Malacca Strait, have said their militaries detected no sign of any unusual aircraft in their airspace.

The massive search operation involving ships and aircraft from 10 countries is spread out over the Gulf of Thailand and the South China Sea, which lie between Malaysia and Vietnam, and in the Strait of Malacca extending into the Andaman Sea.

An Indian foreign ministry official said Malaysia has sought its help in the search. India has a large military command in its Andaman and Nicobar islands and its navy patrols in the Malacca Strait.

ONE OF SEVERAL THEORIES

A senior military officer who had been briefed on the investigation told Reuters on Tuesday that the missing aircraft had made a detour to the west after communications with civilian authorities ended.

‘‘It changed course after Kota Bharu and took a lower altitude. It made it into the Malacca Strait,’’ the officer said.

After the comments from the officer, a non-military source familiar with the investigations said the reported detour was one of several theories and was being checked.

If the plane had made such a detour it would undermine the theory that it suffered a sudden, catastrophic mechanical failure, as it would mean it flew at least 500 km (350 miles) after its last contact with air traffic control.

In the absence of any concrete evidence to explain the plane’s disappearance, authorities have not ruled out anything. Police have said they were investigating whether any passengers or crew on the plane had personal or psychological problems that might shed light on the mystery, along with the possibility of a hijacking, sabotage or mechanical failure.

The airline said it was taking seriously a report by a South African woman who said the co-pilot of the missing plane had invited her and a female companion to sit in the cockpit during a flight two years ago, in an apparent breach of security.

‘‘Malaysia Airlines has become aware of the allegations being made against First Officer Fariq Ab Hamid which we take very seriously. We are shocked by these allegations. We have not been able to confirm the validity of the pictures and videos of the alleged incident,’’ the airline said in a statement.

The woman, Jonti Roos, told Reuters that she and her friend were invited to fly in the cockpit by Fariq and the pilot between Phuket, Thailand, and Kuala Lumpur in December 2011.

‘‘I thought that they were highly skilled and highly competent and since they were doing it that it was allowed,’’ Roos said. ‘‘I want to make it clear, at no point did I feel we were in danger or that they were acting irresponsibly.’’

Hugh Dunleavy, the commercial director of Malaysia Airlines, told Reuters there was no reason to blame the crew.

‘‘We have no reason to believe that there was anything, any actions, internally by the crew that caused the disappearance of this aircraft,’’ he said.

The Boeing 777 has one of the best safety records of any commercial aircraft in service. Its only previous fatal crash came on July 6 last year when Asiana Airlines Flight 214 struck a seawall on landing in San Francisco, killing three people.

U.S. planemaker Boeing has declined to comment beyond a brief statement saying it was monitoring the situation.